docs: add Japanese translate documents (#1812)

* docs: add Japanese documents (`ja/docs`)

* docs: add Japanese documents (`ja/codes`)

* docs: add Japanese documents

* Remove pythontutor blocks in ja/

* Add an empty at the end of each markdown file.

* Add the missing figures (use the English version temporarily).

* Add index.md for Japanese version.

* Add index.html for Japanese version.

* Add missing index.assets

* Fix backtracking_algorithm.md for Japanese version.

* Add avatar_eltociear.jpg. Fix image links on the Japanese landing page.

* Add the Japanese banner.

---------

Co-authored-by: krahets <krahets@163.com>

ja/codes/java/utils/PrintUtil.java

@@ -0,0 +1,116 @@
+/**
+ * File: PrintUtil.java
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+package utils;
+
+import java.util.*;
+
+class Trunk {
+    Trunk prev;
+    String str;
+
+    Trunk(Trunk prev, String str) {
+        this.prev = prev;
+        this.str = str;
+    }
+};
+
+public class PrintUtil {
+    /* 行列を印刷 (配列) */
+    public static <T> void printMatrix(T[][] matrix) {
+        System.out.println("[");
+        for (T[] row : matrix) {
+            System.out.println("  " + row + ",");
+        }
+        System.out.println("]");
+    }
+
+    /* 行列を印刷 (リスト) */
+    public static <T> void printMatrix(List<List<T>> matrix) {
+        System.out.println("[");
+        for (List<T> row : matrix) {
+            System.out.println("  " + row + ",");
+        }
+        System.out.println("]");
+    }
+
+    /* 連結リストを印刷 */
+    public static void printLinkedList(ListNode head) {
+        List<String> list = new ArrayList<>();
+        while (head != null) {
+            list.add(String.valueOf(head.val));
+            head = head.next;
+        }
+        System.out.println(String.join(" -> ", list));
+    }
+
+    /* 二分木を印刷 */
+    public static void printTree(TreeNode root) {
+        printTree(root, null, false);
+    }
+
+    /**
+     * 二分木を印刷
+     * この木プリンターはTECHIE DELIGHTから借用
+     * https://www.techiedelight.com/c-program-print-binary-tree/
+     */
+    public static void printTree(TreeNode root, Trunk prev, boolean isRight) {
+        if (root == null) {
+            return;
+        }
+
+        String prev_str = "    ";
+        Trunk trunk = new Trunk(prev, prev_str);
+
+        printTree(root.right, trunk, true);
+
+        if (prev == null) {
+            trunk.str = "———";
+        } else if (isRight) {
+            trunk.str = "/———";
+            prev_str = "   |";
+        } else {
+            trunk.str = "\\———";
+            prev.str = prev_str;
+        }
+
+        showTrunks(trunk);
+        System.out.println(" " + root.val);
+
+        if (prev != null) {
+            prev.str = prev_str;
+        }
+        trunk.str = "   |";
+
+        printTree(root.left, trunk, false);
+    }
+
+    public static void showTrunks(Trunk p) {
+        if (p == null) {
+            return;
+        }
+
+        showTrunks(p.prev);
+        System.out.print(p.str);
+    }
+
+    /* ハッシュテーブルを印刷 */
+    public static <K, V> void printHashMap(Map<K, V> map) {
+        for (Map.Entry<K, V> kv : map.entrySet()) {
+            System.out.println(kv.getKey() + " -> " + kv.getValue());
+        }
+    }
+
+    /* ヒープを印刷 (優先度キュー) */
+    public static void printHeap(Queue<Integer> queue) {
+        List<Integer> list = new ArrayList<>(queue);
+        System.out.print("ヒープの配列表現:");
+        System.out.println(list);
+        System.out.println("ヒープの木表現:");
+        TreeNode root = TreeNode.listToTree(list);
+        printTree(root);
+    }
+}